Well production method for permafrost zones

ABSTRACT

A method and apparatus for producing a warm fluid from a well through casing, the casing passing through a permafrost zone, wherein the permafrost is insulated from melting by the combined use of vacuum and solid thermal insulation.

O United States Paten 1191 1111 3,720,267 Allen et a1. 1March 13, 1973541 WELL PRODUCTION METHOD FOR 3,142,336 7/1964 Doscher ..166/57 xPERMAFROST ZONES 3,380,530 4/1968 McConnell et a1. ....l66/57 xInventors: William G. AllenJames A. L velle, 3,397,745 8/1968 Owens eta1. ..166/57 Frank J Sch-uh a of Dallas Tex 3,613,792 10/1971 Hyde etal. ..166/3l5 3,642,065 2/1972 Blount ..166/244 R [73] Assignee:Atlantic Richfield Company, New 3,650,327 3/1972 Burnside ..166/303York, NY.

Filed: p i 5, 972 Primary ExaminerStephen J. Novosad 3 Attorney-BlucherS. Tharp et a1 21 Appl. No-.: 241,131

Related u.s. Application Data 57 1 ABSTRACT [62] Division of Ser. No.77,647, Oct. 2, 1970, Pat. No. A method d apparatus f producing a warmfl id 36801631' from a well through casing, the casing passing through apermafrost zone, wherein the permafrost is insulated gigz gb frommelting by the combined use of vacuum and 58 Field of Search ..l66/3l4,315, 57,1)1o. 1, sohd thermal msulaton' [56] References Cited 4 Claims,5 Drawing Figures UNITED STATES PATENTS 1,413,197 4/1922 Swan ..166/57PATENTEUHAR 1 31015 FIG. I

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WELL PRODUCTION METHOD FOR PERMAFROST ZONES CROSS REFERENCE TO RELATEDAPPLICATIONS This application is a division of application Ser. No.77,647, filed Oct. 2, 1970, now U.S. Pat. No. 3,680,631.

BACKGROUND OF THE INVENTION Heretofore in the production of warm fluidsuch as petroleum gas and/or petroleum liquid from a wellbore in theearth through a permafrost zone whereby part of the permafrost could bemelted upon continued expo sure to the warm fluid, it has been proposedto coat or otherwise surround the casing or tubing (pipe) in thewellbore with solid thermal insulation such as polyu rethane foam. Theinsulation normally extends from the earths surface down to the bottomof the permafrost zone in a continuous cylindrical form.

Thermal insulation applied in this manner to the outside of easing ortubing is expensive to apply to each a joint of the pipe as it passesinto the wellbore because it takes-up the time of the rig and theworkmen to apply the insulation. The insulation is quite fragile underthe normal conditions in which pipe of any type is inserted into awellbore and, therefore, is likely to be at least partially scraped orotherwise broken off from the pipe before the pipe is set into its finalposition in the wellbore. Further, some insulation, particularly theporous type of insulation, does not act as efficiently in a wellbore ifliquid, which is almost always present in a wellbore, penetrates thepores of the insulation.

Thus, it is highly desirable to have an efficient type of insulationwhich is quite durable under normal operating and pipe emplacementconditions on a well so that one can be certain that the insulation isintact when the pipe is emplaced in its final position in the wellboreand which does not take up an undue amount of time of the rig andpersonnel when running the pipe into the wellbore.

SUMMARY OF THE INVENTION According to this invention all of the aboverequirements are met by minimizing the amount of solid insulation usedand physically protecting the minor amount of solid insulation that isused.

According to this invention, apparatus wherein each section of casing,tubing, or other pipe which is desirably insulated in the permafrostzone of the wellbore, hereinafter referred to collectively as casing, isprovided with a vacuum chamber for substantially the complete length ofeach section of easing but which vacuum chamber terminates a finitedistance short of either end of each section of easing so that whensections of easing are joined one to another there is an area ofrelatively uninsulated space where the two sections of casing are joinedone to another. Solid insulation is employed in these relatively smalluninsulated spaces, and is protected by the configuration of the,

vacuum chamber itself or holding members or both.

This invention also relates to a method of producing a warm fluidthrough a casing zone in a wellbore in the earth, the wellbore passingthrough a zone of permafrost that can be melted in part upon continuedexposure to the warm fluid wherein there is provided a plurality ofspaced apart vacuum zones along the length of the casing zone in thepermafrost zone. There is thus established a plurality of vacuum zoneswherein each pair of adjacent vacuum zones has an uninsulated spacetherebetween and there is provided in at least one of these uninsulatedspaces a solid insulation material to provide substantially continuousinsulation of the vacuum or solid type throughout the permafrost zone.Thereafter the warm fluid is produced through the thus insulated casingzone to the earths surface.

This invention provides a .method and apparatus whereby fluids hotenough to melt permafrost can be continuously produced through apermafrost zone for a long period of time such as 20 years withoutsubstantially melting the permafrost itself.

Accordingly, it is an object of this invention to provide a new andimproved method and apparatus for producing wells through a permafrostzone. It is another object to provide a new and improved method andapparatus for thermally insulating pipe in a wellbore, It is anotherobject to provide a new and improved method and apparatus for producinghot fluid through permafrost without substantially melting thepermafrost. It is another object to provide a new and improved methodand apparatus for thermally insulating at least part of a wellbore in amanner wherein the insulation will stand up under normal handling andemplacement of casing and the like in the wellbore.

Other aspects, objects, and advantages of this invention will beapparent to those skilled in the art from this disclosure and theappended claims.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 shows a cross-section of awellbore containing a permafrost zone and with casing emplaced thereinin accordance with this invention.

FIGS. 2 through 5 show cross-sections of various embodiments within thisinvention for arranging the vacuum chambers, the solid insulation in theuninsulated areas where two sections of casing are joined, and variouscoupling means.

More specifically, FIG. 1 shows the earths surface 1 with a wellbore 2drilled therein, the bottom of the wellbore not being shown for sake ofbrevity. Wellbore 2 passes through a tundra zone 3 :at the earthssurface which extends downwardly a short distance of, for example, 2feet to a permafrost zone 4. Below zone 4 is unfrozen earth zone 5.

A casing string 6, which can be one or more strings of concentric pipe,is shown to be composed of, for simplicity, three individual sections ofeasing denoted by references numerals 7, 8, and 9. Casing section 7, thetop of which is not shown, is fixed to a conventional wellhead (notshown) which is well known in the art and which extends downwardly intothe permafrost zone and terminates at joint line 10.

Casing section 8 starts at line 10 and extends downwardly to joint line11. Casing sections 7 and 8 contain annular vacuum chambers 12 and 13,respectively. These chambers terminate a finite distance from the endsof each section so that, for example, when sections 7 and 8 are joinedas represented by line 10 there is a finite distancel4 of substantiallyuninsulated casing space. Uninsulated space 14 contains solidinsulation, as will be shown hereinafter in detail.

Casing sections 7 and 8 are joined to one another by each threading intoa conventional sleeve type coupling 15 which is well known in the art.Casing sections 8 and 9 are also joined at line 11 by sleeve coupling16.

Casing section 9 starts at line 11 and extends downwardly out of thepermafrost zone 4 into the unfrozen zone and there is cemented in by wayof cement 17 so that it supports casing sections 7 and 8 and thewellhead.

FIG. 2 shows an enlarged cross-section of the bottom portion of easingsection 7 and an upper portion of casing section 8 including uninsulatedsection 14. Space 14 is shown in FIG. 2 to contain an annular, rightcylindrical section 20 of solid thermal insulation to provide continuityof insulation from vacuum chamber 12 to vacuum chamber 13.

In FIG. 2 casing sections 7 and 8 are shown to have main walls 21 and22, respectively. Vacuum chambers 12 and 13 extend inwardly from mainwalls 21 and 22 as provided by an inwardly extending annular ring 23which defines the lower end of chamber 12 and which has a matchingmember (not shown) enclosing the top of chamber 12. The inner surface ofchamber 12 is closed between the lower-and upper annular rings by way ofannular, right cylindrical sleeve 24.

Sleeve 24 has an extension member 25 which extends from the lower end 23of vacuum chamber 12 towards the nearest end of casing section 7, i.e.,line 10. Member 25 is spaced inwardly from main wall 21 to provide aslot for insertion of insulation 20. This slot holds insulation 20 inplace and protects the insulation from material passing through theinterior of the casing. Depending upon the amount of protection desired,member 25 can extend substantially to line or any desired distance fromring 23 towards line 10.

Insulation can extend into contact with either or both of rings 23 and26. Alternatively an annular insulation material such as rubber can beinserted between insulation 20 and rings 23 and 26 as represented byannular ring inserts 32 and 32. Inserts 32 and 32' can provide a sealagainst thermal convection currents.

Vacuum chamber 23 is similarly configured with an inwardly extending,upper, annular ring 26 which is the same type of ring which constitutesthe upper ring for chamber 12. Ring has a ring similar to ring 23 (notshown) forming the bottom end of chamber 13 and these two rings arejoined by innersleeve 27 to define closed chamber 13. Ring 26 hasopenable port 28 therein by means of which a vacuum can be pulled in theinterior of chamber 13. This is also true for the upper ring of chamber12. Innersleeve 27 also has an extension member 29 which provides thesame functions as described hereinabove for member 25.

It should be noted that insulation 20, instead of occupying only part ofthe lateral space between members 25 and 29 and main walls 21 and 22,respectively, can be sized to substantially completely fill this space.

Vacuum chambers 12 and 13 can be substantially vacant of any matter orcan have placed therein additional solid or liquid thermal insulatingmaterial or other types of insulating material, such as radiantinsulating material, as desired. For example, one or more layers ofsolid insulating material can be emplaced in chambers 12 and 13 asrepresented by 30 and 31. This additional insulation at least partiallyfills the vacuum chambers. The one or more layers of insulating materialcan be alternated with thermal insulation and other types of insulationas desired.

FIG. 3 shows the joined area of two adjacent sections of casing such asthat shown in FIGS. 1 and 2 and as represented by upper and lower casingsections 33 and v 34 joined at line 35 by conventional sleeve typecoupling 36.

However, one difference in configuration in FIG. 3 is that main walls 37and 38 carry outwardly extending vacuum chambers 39 and 40 instead ofinwardly extending chambers 12 and 13 of FIGS. 1 and 2. Chambers 39 and40 can also be empty or contain one or more layers of solid and/orliquid insulation materials 41 and 42.

Chamber 39 is defined by an outwardly extending lower, annular, end ring43 which contains a vacuum port 44 and which before welding is integralonly with transition piece 37 of wall 37. Sleeve 45 extends from weld 52to a similar upper weld (not shown).

Member 46 extends downwardly from sleeve 45 towards the nearest end ofcasing section 33 to provide a holding and protection member for anannular, right cylindrical ring of solid insulation material 47.

Outwardly extending chamber 40 is composed of an upper annular ring 48which before welding is integral only with transition piece 38 of innersleeve 38, outer sleeve 49 being welded at the bottom of a weld similarto weld 52 to form the enclosed chamber 40. Ring 48 is substantially thesame as the upper rig which closes chamber 39. Extension member 50 isprovided in the same manner and for the same reasons as member 46. Hereagain members 46 and 50 can extend toward line 35 any desired length,depending upon the desired amount of protection for insulation 47 andthe ease with which insulation 47 can be put in place. It should benoted also that insulation 47 has a notched out portion 51 whichaccommodates coupling 36.

FIG. 3 also shows welds 52 through 57, inclusive. This makes parts 45',37, 38, and 49 severable from the casing section walls 45, 37, 38, and49, respectively. Parts 45', 37', 38', and 49' are transition pieceswhich constitute a type of tool joint, parts 45 and 49' being inaddition transition piece spacers due to the spacing function of members43 and 48.

There are distinct advantages in the fabrication of the overall casingsection by having severable tool joints. In assembling casing section33, wall section 45 and 37 are initially separate and are composed of aconventional casing steel whose strength and other desirablemetallurgical characteristics deteriorate when exposed to extreme heatsuch as that encountered in welding operations. In the first step ofassembly pieces 45 and 37' are welded at 52 and 53 to 45 and 37,respectively, but are not yet welded at 54. Similar steps are taken atthe opposite end (not shown) of section 33. After making welds 52 and53, the still separate section 45 and 37 with transition pieces at bothends are both heat treated at both ends to restore the strength andother desired metallurgical characteristics to the portions of 45 and 37adversely affected by the heat of welding at 52 and 53. Thereafterinsulation 41 can be wrapped around the outside of 37 between ring 43and the opposing ring at the opposite end of 37 (not shown but the sameas ring 48) if it is desired to have additional insulation in chamber39.

Then separate subassemblies 45 and 37 with their transition pieces areassembled as shown in FIG. 3 and final weld 54 made, a similar finalweld such as 55 being made at the opposite end of 33. The metallurgicalcomposition of transition pieces 45' and 37' is chosen so thatdeterioration, if any, of strength or other desired properties broughtabout by the heat involved in making weld 54 does not fall below theminimum strength and other properties of walls 45 and 37. Insulation 41can be protected from the heat of final welds such as 54 by spacing theinsulation 41 away from the end rings such as 43, inserting insulationrings such as asbestos between insulation 41 and the end rings, and thelike.

It can be seen from the above that by use of severable, weldabletransition pieces of selected metallurgical composition the fabricationof each casing section can be greatly facilitated with adverse effect onthe strength etc. of the casing used in the fabrication operation. Thus,commercially available casing pipe can be used in making the casingsections of this invention.

FIG. 4 shows yet another embodiment within the scope of this inventionwherein upper and lower casing sections 60 and 61 are threadably joinedwith one another by means of a pin 62' and box means 63' in lieu of theseparate couplings or 36.

FIG. 4 shows internally extending, empty vacuum chambers 64 and 65.Chamber 64 is defined by a lower ring 66, with vacuum port 67, part oftransition piece 68, the top of chamber 64 being enclosed by a similarupper annular ring. It should be noted that the upper and lower annularrings can be substantially perpendicular to the main wall of the casingsection as shown in FIG. 2 or at any desired inclination such as thatshown 'in FIG. 4. Similarly, chamber 65 is defined by an upper annularring 69 an integral part of transition piece 70' and enclosed by meansof a lower annular ring similar to ring 66. Both sleeves 68 and 70 carryextension members 71 and 72 as means for protecting solid insulation 73and for holding that insulation in place.

FIG. 4 shows that pin and box type connections are amenable to the tooljoint welding fabrication procedure disclosed in FIG. 3. In FIG. 4 aconventional tool joint composed of pieces 62' and 63' is welded to 62and 63 with welds 74 and 78. Similarly, transition spacer pieces 68 and70 are welded to 68 and 70 with welds 75 and 79. The two subassembliesare welded to one another with final welds 76 and 77. The steps offabrication are the same as explained for FIG. 3 in that heat treatingafter welding subassemblies such as at 74, 75, 78, and 79, etc. iscarried out to restore strength etc. lost by the welding after which thesubassemblies are joined with final welds such as 76 and 77 to completethe casing section with welding, without further heat treating, andwithout adversely reducing the physical properties of the transitionpieces below the same properties of 62, 68, 63, and 70.

FIG. 5 shows upper and lower casing sections 80 and 81 having pin andbox joinder members 82 and 83, respectively. Outer vacuum chambers 84and 85 are defined in the same manner as prior chambers, the bottomportion of chamber 84 being defined by an annular ring 86 extendinglaterally outward from the main wall of pin 82 and joined at its outerend to sleeve 87.

Similar explanation applies to the upper portion of chamber with upperperpendicular ring 88 and sleeve 89. The uninsulated space along members82 and 83 between rings 86 and 88 carries annular right cylindricalinsulation 90 having a cutout portion 91 for members 82 and 83. Ring 88has a vacuum port 96.

FIG. 5 shows that the outer walls 87 and 89 of chambers 84 and 85,respectively, can provide protection for insulation 90 so thatinsulation 90 can be glued, taped or otherwise attached to the casingsections without the use of extension members. The: extension memberssuch as members 46 and 50 can be eliminated because of the protectivefunction of the outwardly extending vacuum chambers themselves.

An alternative holding member for insulation 90 or the insulation of anyof FIGS. 1 through 4, can be a metal sleeve around the periphery of 90and overlapping walls 87 and 89. In this manner a relatively fragileinsulation can be used for 90 and still not be damaged duringtransportation or emplacement. If it is desired to keep fluids from 90an outer heat shrinkable sleeve of, for example, polyethylene orpolypropylene can be shrunk around the outside of insulation 90 or ametal sleeve surrounding 90.

One or more of the interior surfaces of the vacuum chambers can becoated with a gas diffusion barrier such as a plating of nickel orchromium or alloys thereof. This barrier prevents gas from diffusingthrough one or more of the walls of the vacuum chamber into itsevacuated interior. Gas diffusion into the interior of a vacuum chambercould reduce the magnitude of the vacuum in the chamber. Chambers 84shows a diffusion barrier 92 on all the interior surfaces thereof.Chamber 85 shows a diffusion barrier 93 on two of the three interiorsurfaces shown. All or any lesser number of interior surfaces can becoated with one or more diffusion barriers as desired.

If desired, a corrosion barrier such as stainless steel can be employedon the outside and/or inside surfaces of the casing section which willcontact packer fluids, cement, drilling mud, and the like to prevent,for example, corrosion of the casing and the formation of hydrogen whichmay diffuse into the vacuumchamber.

The apparatus shown in FIGS. 1 and 5 can be fabricated and welded in thesame manner disclosed for FIGS. 3 and 4, if desired.

The solid insulation employed in this invention in the interior of thevacuum chambers or the uninsulated space between adjacent casing sectioncan be any material which is substantially nonporous, or contains pores,bubbles, voids, and the like, or is composed of 2 or more separatelayers of materials, etc. By solid what is meant therefore is anyinsulating material which will maintain its shape although not confinedon all sides. This is shown in FIGS. 2 through 5 for insulation 20, 47,73, and 90. Suitable insulation include polymers such as polyvinylchloride, polyethylene, polypropylene, foamed polyethylene, foamedpolypropylene, nylon, polytetrafluoroethylene, polyurethane, asbestos,and the like.

Rings 23, 26, 43, 48, 66, 86, etc. and any other element which providesa path for heat flow around the vacuum chambers can be made oflowthermal conduc tivity metal such as certain stainless steels or even ofnonmetal thermal insulation or a combination thereof.

When the vacuum chambers extend inwardly from the main wall of thecasing section they 'can extend quite close to both ends of the casingsection although there is always some slight space where two adjacentsections of casing are joined in which space there is no vacuum chambercoverage. For this space there should be provided solid insulation asdisclosed hereinabove.

When the vacuum chambers extend on the outside of the main wall of thecasing section the ends of the vacuum chambers cannot as closelyapproach the ends of the casing section as when the vacuum chambersextend inwardly from the main wall. This is so because in the normalhandling of casing for emplacement of same in the wellbore, varioustools such as slips, tongs, and the like are employed which grip theexternal surface of the casing in a rough and forceful manner. In orderto prevent damage to the outwardly extending vacuum chambers, thesechambers terminate a finite distance from both ends of a given casingsection to provide an exposed length of main casing wall, such as length95 in FIG. 3, so that either end of the casing section can be graspedwith slips, and the like without damaging the external vacuum chamber.This requirement will have a limiting value on the length of extensionmembers 46 and 50. Thus, allowance should be made at both ends ofoutwardly extending vacuum chambers for the emplacement of working toolson the main wall of the casing section adjacent both ends of thatsection.

If desired, conventional gas absorbing material sometimes called gettermaterials can be employed in the interior of the vacuum chambers toabsorb any gas that may leak or diffuse into the vacuum chamber duringuse so that the magnitude of vacuum initially imposed upon that chambercan be substantially maintained. Any conventional getter can beemployed, e.g., PdO on a dessicant, molecular sieve, and the like.

According to the method of this invention, a warm fluid such aspetroleum gas and/or liquid which is at a temperature which can meltpermafrost upon continued exposure, i.e., at a temperature greater than32F, preferably at least about lF., is pumped from the bottom of thewell to the earths surface through the casing, including that part ofthe casing that passes through the permafrost zone. The pumping can becar-' ried out for an extended length of time while the temperature atthe permafrost face 2 of the wellbore is no greater than 32F., moregenerally in the range of from about 14 to about 32F.

The improvement in this production method comprises providing aplurality of spaced apart vacuum zones such as zones 12 and 13 of FIG. 1along the length of the casing zone in the permafrost zone therebyestablishing a plurality of vacuum zones wherein each pair of adjacentvacuum zones has therebetween an uninsulated space such as area 14 ofFIG. 1. Thereafter providing in at least one of these uninsulated spacesbetween adjacent vacuum zones a solid insulation materialforsubstantially continuous insulation by either vacuum or solidinsulation throughout the length of the permafrost zone, and producingthe warm fluid through the casing zone to the earths surface. 1

The vacuum employed can vary widely depending upon the desiredinsulating effect but will generally be in the range of from about 100to about 10*, preferably from about 10 to about 10' millimeters ofmercury.

EXAMPLE Steel casing for an oil well having a pin and box typeconnections and interiorly extending empty vacuum chambers substantiallyas shown in FIG. 4 is employed. In-the casing, 9% inch outside diameterC75 API casing in 40 foot lengths is used as the outside walls while theinnersleeves 68 and 70 of FIG. 4 are 7 inch outside diameter C- APIcasing steel. The 9% inch casing has a 0.395 inch wall thickness whilethe 7 inch casing has a 0.317 inch wall thickness. The annular spacebetween the 7 inch and 9% inch casings, being the annular space forvacuum chambers 64 and 65 is 1.835 inches. A vacuum of about l0"millimeters of mercury is imposed in these chambers with only airremaining.

Solid insulation 73 is a right cylindrical block of solid polyvinylchloride having a wall thickness of about 1 inch and a height of about4% inches.

This apparatus is employed in a permafrost zone hav ing a temperature atthe face of the permafrost in the wellbore in the range of 14 to 32F.Liquid petroleum oil at a temperature of about 160F. is pumped throughthe interior of the 7 inch casing for at least 1 year withoutsubstantial melting of the permafrost face which is approximately 5inches from the 9% inch casmg.

Reasonable variations and modifications-are possible within the scope ofthis disclosure without departing from the spirit and scope of thisinvention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. In a method for producing a warm fluid through a casing zone in awellbore in the earth, the wellbore passing through a zone of permafrostthat can be melted in part upon continued exposure to said warm fluid,the improvement comprising providing a plurality of spaced apart vacuumzones along the length of said casing zone in said permafrost zonethereby establishing a plurality of vacuum zones wherein each pair ofadjacent vacuum zones has an uninsulated space therebetween, providingin at least one of said uninsulated spaces between adjacent vacuum zonesa solid insulation material to provide substantially continuousinsulation through said permafrost zone, and producing said warm fluidthrough said casing zone to the earthsurface.

2. A method according to claim 1 wherein said vacuum zones haveestablished therein a vacuum in the range of from about to about 10millimeters of mercury.

3. A method according to claim 2 wherein said warm fluid is at least oneof petroleum oil and petroleum gas at a temperature greater than 32F.,and the temperature at the permafrost face of said well bore is nogreater than 32F.

4. A method according to claim 2 wherein said warm fluid is at atemperature of at least about 100F. when passing through said permafrostzone.

1. In a method for producing a warm fluid through a casing zone in awellbore in the earth, the wellbore passing through a zone of permafrostthat can be melted in part upon continued exposure to said warm fluid,the improvement comprising providing a plurality of spaced apart vacuumzones along the length of said casing zone in said permafrost zonethereby establishing a plurality of vacuum zones wherein each pair ofadjacent vacuum zones has an uninsulated space therebetween, providingin at least one of said uninsulated spaces between adjacent vacuum zonesa solid insulation material to provide substantially continuousinsulation through said permafrost zone, and producing said warm fluidthrough said casing zone to the earth''surface.
 1. In a method forproducing a warm fluid through a casing zone in a wellbore in the earth,the wellbore passing through a zone of permafrost that can be melted inpart upon continued exposure to said warm fluid, the improvementcomprising providing a plurality of spaced apart vacuum zones along thelength of said casing zone in said permafrost zone thereby establishinga plurality of vacuum zones wherein each pair of adjacent vacuum zoneshas an uninsulated space therebetween, providing in at least one of saiduninsulated spaces between adjacent vacuum zones a solid insulationmaterial to provide substantially continuous insulation through saidpermafrost zone, and producing said warm fluid through said casing zoneto the earth''surface.
 2. A method according to claim 1 wherein saidvacuum zones have established therein a vacuum in the range of fromabout 100 to about 10 5 millimeters of mercury.
 3. A method according toclaim 2 wherein said warm fluid is at least one of petroleum oil andpetroleum gas at a temperature greater than 32*F., and the temperatureat the permafrost face of said well bore is no greater than 32*F.